Hammer

• 1. Introduction

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  A hammer is a weighted head fixed to a long handle, swung to deliver an impact to a small area of an object. With it, a person can drive nails into wood, shape metal at a forge, or crush rock. Great strength is not required. The tool itself does the amplifying. The archaeological record suggests it may be the oldest tool for which definite evidence exists, and its lineage may stretch back roughly 3.3 million years. How does a simple weighted head turn the muscles of an arm into a force strong enough to bend steel? Why have toolmakers produced over 40 different types? And why do thunder gods, mining symbols, and a civil rights anthem all reach for the same object? The answers begin with a deposit of shaped stones beside a lake in Kenya.

• 2. The Oldest Tool

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  Near Kenya's Lake Turkana, Sonia Harmand and Jason Lewis of Stony Brook University made a find in 2012 that pushed the hammer's story back about 3.3 million years. While excavating, they uncovered a very large deposit of variously shaped stones, including ones used to strike wood, bone, or other stones to break them apart and shape them. The first hammers were made without handles, simple striking stones held in the hand. By about 30,000 BCE, during the middle of the Paleolithic Stone Age, stones were being attached to sticks with strips of leather or animal sinew. Adding a handle gave the user better control and fewer accidents. With that control, the hammer became the primary tool used for building, food, and protection, the device a person reached for to make a shelter or defend it.

• 3. Anatomy Of A Blow

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  A traditional hand-held hammer has two parts, a separate head and a handle, fastened together by a special wedge, by glue, or by both. The head is typically steel that has been heat treated for hardness, while the handle, also called a haft or helve, is usually wood or plastic. The two-piece design lets a dense metallic striking head pair with a non-metallic, shock-absorbing handle that reduces user fatigue from repeated strikes. When wood is used, it is often hickory or ash, tough and long-lasting materials that dissipate the shock waves traveling down from the head. Rigid fiberglass resin offers an alternative that does not absorb water or decay, though it does not dissipate shock as well as wood. A loose head is treated as a serious hazard, because it can detach mid-swing and fly off as an uncontrolled projectile. For that reason, worn wooden handles can be replaced using specialized kits that cover a range of sizes and designs, complete with wedges and spacers for secure attachment. The high elasticity of the steel head matters too, especially when it works against an equally elastic anvil to transfer energy cleanly.

• 4. A Tool For Every Trade

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  The claw hammer, ubiquitous in framing, carries a claw to pull nails back out of wood, and it sits in most household toolboxes across North America. Names multiply from there. A large hammer-like tool is a maul, sometimes called a beetle, a wood- or rubber-headed version is a mallet, and one fitted with a cutting blade is usually a hatchet. The shapes follow the work. A ball-peen hammer ends in a ball on the face opposite its striking surface, and some upholstery hammers carry a magnetized face to pick up tacks. A drilling hammer, a short-handled sledgehammer with a 2 to 4 lb head and a 10 in handle, earned the name single-jack because one person could swing it while holding a chisel in the other hand. An engineer's hammer, weighing 2 to 4 lbs with a 12 to 14 inch handle, was once an essential part of a railroad engineer's toolkit for working on steam locomotives. Trades have generated dozens more, among them the bricklayer's hammer, the geologist's rock pick, the blacksmith's rounding hammer, the dead blow hammer with its sand-or-pellet-filled head, and the gavel that judges and presiding authorities use to draw attention. Beyond the human arm lie powered relatives, the jackhammer, the steam hammer, the trip hammer, the nail gun, built to deliver forces no arm could match.

• 5. The Hidden Physics

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  A hammer is a simple force amplifier. During the swing, the head stores kinetic energy equal to the length of the swing times the force from the arm and gravity. At impact, the target stops the head within a very short distance, especially if the object is hard, heavy, or resting on an anvil. Because the stopping force times that tiny distance must equal the head's stored energy, the force at the moment of contact becomes far greater than the muscle force that started the swing. The energy delivered equals one half the head's mass times the square of its speed at impact. Mass adds energy in a straight line, but speed adds it as a square, which is why velocity matters so much. High-tech titanium heads exploit this. Lighter than steel, they allow longer handles and higher head speed, delivering the same energy with less arm fatigue. A titanium head returns about 3 percent recoil energy, while a steel head can return up to 30 percent, and dead blow hammers use rubber or steel shot to soak up recoil rather than bounce. Gravity tilts the balance as well. Hammering downward, it adds acceleration and energy; hammering upward, it subtracts both. Traditional mechanical pile drivers lean on this entirely, relying on gravity alone for the down stroke.

• 6. Handles And Hazards

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  The handle keeps a user's hands away from the point of impact and gives the hand a broad area to grip. Most importantly, it lets the user maximize the head's speed on each blow. Length is a balancing act. The first constraint is space, which is why sledgehammers, swung in open ground, carry handles far longer than a carpenter's. The second is subtler, since a longer handle is harder to guide to its target at full speed. Too long and the hammer wastes force off-target; too short and it cannot deliver enough force, demanding more blows. The tool also carries real risks. Awkward handles can cause repetitive stress injury to hand and arm joints, and uncontrolled shock waves can injure nerves and the skeleton. Both manual and powered hammers can cause peripheral neuropathy when used improperly. Striking metal can throw small projectiles that lodge in the eye, which is why safety glasses are recommended. Sparks raise a separate danger. The impact between steel heads and struck objects can ignite flammable or explosive gases, a hazard in underground coal mining, where methane is present, and in petroleum refineries and chemical plants. In those settings, non-sparking tools made of aluminium or beryllium copper take the steel hammer's place.

• 7. The Hammer As Emblem

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  Being one of the most used tools by humankind, the hammer turns up constantly in flags and heraldry. In the Middle Ages it appeared in blacksmith guild logos and family symbols, and the hammer and pick stands for mining. In mythology the Norse god Thor wields a hammer named Mjolnir, while the Celtic and Gallo-Roman god Sucellus and the Greek hero Hercules each carried hammers in their lore. Many decorative hammer artifacts have been found, and modern practitioners of the Norse religion often wear reproductions as a sign of faith. In American folklore, the hammer of John Henry stands for the strength and endurance of a man. The Workers' Party of Singapore built its logo on a hammer to symbolize civic nationalism and social democracy. The hammer and sickle, symbol of the former Soviet Union and tied to communism and early socialism, uses the hammer for the industrial working class and the sickle for the agricultural one. The same hammer appears in some coats of arms of former socialist states like East Germany, while the Hammer and Sword stands for Strasserism, and the Workers' Party of Korea adds an ink brush to represent Juche and Songun. In Pink Floyd's The Wall, two crossed hammers mark the fascist takeover during In the Flesh, beating down any nails that stick out. Judah Maccabee was nicknamed The Hammer, possibly for his ferocity in battle, and the name Maccabee may derive from the Aramaic maqqaba. The hammer in the song If I Had a Hammer carries a relentless message of justice across the land, and the song became a symbol of the civil rights movement.